Issue |
A&A
Volume 460, Number 1, December II 2006
|
|
---|---|---|
Page(s) | 59 - 66 | |
Section | Extragalactic astronomy | |
DOI | https://doi.org/10.1051/0004-6361:20065431 | |
Published online | 12 September 2006 |
Warm-hot intergalactic medium contribution to baryonic matter
Nicolaus Copernicus Astronomical Center, Bartycka 18, 00-716 Warsaw, Poland e-mail: soltan@camk.edu.pl
Received:
13
April
2006
Accepted:
10
August
2006
Context.Hydrodynamical simulations indicate that a substantial fraction of baryons in the universe remains in a diffuse component – warm-hot intergalactic medium (WHIM).
Aims.The goal of this paper is to determine the physical properties (spatial distribution, temperature, and density) of the WHIM.
Methods.Spatial structure of the soft extended X-ray emission surrounding field
galaxies is carefully investigated using the XMM-Newton EPIC/MOS observations.
Angular correlations between the galaxy distribution and
the soft X-ray background extending over several arcmin result from the
large-scale clustering of galaxies. At small angular scales
(below ), the excess of the soft flux is interpreted as
the genuine emission from
halos of the WHIM surrounding individual galaxies.
Results.Bulk parameters of the average WHIM halos associated with galaxies in
the sample are estimated. A typical halo has a characteristic radius of
Mpc and a mass of
. The average
density of the WHIM detected in soft X-rays in the local universe,
, amounts to
g cm-3 (
%).
The range of uncertainties reflects both the statistical scatter of
the investigated correlations and our poor knowledge of the WHIM characteristics
(e.g., metallicity). It is possible that the actual uncertainties are larger.
Conclusions.Observations of the X-ray WHIM emission are in good agreement with the numerical
simulations, but accuracy of the observational material is insufficient to
constrain the theory of WHIM. A series of deep observations of a moderately
numerous sample of low redshift galaxies with high resolution instruments
of would significantly improve our estimates of the WHIM
parameters.
Key words: X-rays: diffuse background / intergalactic medium / X-rays: galaxies
© ESO, 2006
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